<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>demo-生成印章</title>
</head>
<body>
    <div>
        <label for="stamp">公司名称</label><input type="text" id="stamp" />
        <br />
        <label for="stamp">下面的小字</label><input type="text" id="small" />
        <br />
        <button id="btn">生成</button>
    </div>
    <canvas id="canvas" width="250" height="250"></canvas>
</body>
<script>
    function createSeal(id,company,name){

        var canvas = document.getElementById(id);
        var context = canvas.getContext('2d');

        // 绘制印章边框
        var width=canvas.width/2;
        var height=canvas.height/2;
        context.lineWidth=7;
        context.strokeStyle="#f00";
        context.beginPath();
        context.arc(width,height,110,0,Math.PI*2);
        context.stroke();

        //画五角星
        create5star(context,width,height,30,"#f00",0);

        // 绘制印章名称
        context.font = '22px Helvetica';
        context.textBaseline = 'middle';//设置文本的垂直对齐方式
        context.textAlign = 'center'; //设置文本的水平对对齐方式
        context.lineWidth=1;
        context.fillStyle = '#f00';
        context.fillText(name,width,height+65);

        // 绘制印章单位
        context.translate(width,height);// 平移到此位置,
        context.font = '30px Helvetica'
        var count = company.length;// 字数
        var angle = 4*Math.PI/(3*(count - 1));// 字间角度
        var chars = company.split("");
        var c;
        for (var i = 0; i < count; i++){
            c = chars[i];// 需要绘制的字符
            if(i==0)
                context.rotate(5*Math.PI/6);
            else
                context.rotate(angle);
            context.save();
            context.translate(90, 0);// 平移到此位置,此时字和x轴垂直
            context.rotate(Math.PI/2);// 旋转90度,让字平行于x轴
            context.fillText(c,0, 5);// 此点为字的中心点
            context.restore();
        }

        //绘制五角星
        /**
         * 创建一个五角星形状. 该五角星的中心坐标为(sx,sy),中心到顶点的距离为radius,rotate=0时一个顶点在对称轴上
         * rotate:绕对称轴旋转rotate弧度
         */
        function create5star(context,sx,sy,radius,color,rotato){
            context.save();
            context.fillStyle=color;
            context.translate(sx,sy);//移动坐标原点
            context.rotate(Math.PI+rotato);//旋转
            context.beginPath();//创建路径
            var x = Math.sin(0);
            var y= Math.cos(0);
            var dig = Math.PI/5 *4;
            for(var i = 0;i< 5;i++){//画五角星的五条边
                var x = Math.sin(i*dig);
                var y = Math.cos(i*dig);
                context.lineTo(x*radius,y*radius);
            }
            context.closePath();
            context.stroke();
            context.fill();
            context.restore();
        }
    }

    function newStamp(){
        var text = document.getElementById('stamp').value;
        var textSmall = document.getElementById('small').value;

        var canvas = document.getElementById('canvas');
        canvas.height += 1;
        createSeal('canvas',text,textSmall);
    }

    document.getElementById('btn').onclick = newStamp;

    createSeal('canvas','株洲市泽林网络科技有限公司','测试专用章');

</script>
</html>